Gas generated through the decomposition of waste in landfills consists primarily of methane, along with volatile organic compounds. The volatile organic compounds can consist of hydrocarbons, which are relatively inert, or can be halogenated compounds containing chlorine, bromine, fluorine, or iodine, which are reactive. In addition, the volatile organic compounds may include aromatic hydrocarbons, such as benzene, toluene, xylene, and the like, which are classified as carcinogenic. The type and concentration of the volatile organic compounds can vary from site-to-site, depending upon the nature of the waste in the landfill.
It has been the practice, in the past, to vent the gas from the landfill. In a typical installation, a number of perforated wells or pipes are distributed throughout the landfill to collect the gas, and the gas is then conducted to a manifold or header for discharge from the landfill. As the landfill gas consists primarily of methane, it has been proposed to use the landfill gas as a fuel for gas aspirated internal combustion engines. The engines can be used at the landfill site for generating electricity or steam, pumping, or other functions. At a typical landfill there may be from two to six engines that are operating on the landfill gas.
The presence of certain volatile organic compounds in the landfill gas, particularly the halogenated compounds, can cause serious problems with the operation of internal combustion engines, Due to the reactivity of these compounds, they can react with other constituents to form acids which can attach or corrode engine bearings, bushings, valve guides and stems, as well as producing deposits on the valve seats, and deterioration of the engine oil.
Because of these potential problems with the use of landfill gas, there is a need for an efficient method for removing these volatile organic substances from the landfill gas.